1. Field of the Invention
The present invention relates to a protrusion pattern forming device with a display function not only forming a pattern of protrusions such as Braille characters but also being able to display a pattern of dots.
2. Description of the Related Art
As a continuation of barrier-free or universal design, in recent years, Braille characters or others for a similar use are often provided along, and thus are of great help to people with visual impairments in their daily lives. The Braille characters are each configured by protruding points arranged under a predetermined rule on the surface of an object to be touched by human fingers or others, and thereby each being assigned meaning or representing numbers. On the other hand, the others for a similar use as the Braille characters are not those directly assigned meaning or representing numbers, but are for various purposes including object identification, information transmission, and others. The others for such a use are found on Japanese bank notes and textured paving blocks provided on roads for guiding pedestrians, for example.
With the recent widespread use of a personal digital assistant (PDA), such a PDA is expected to be provided with various types of additional functions. As one example, the PDA may be provided with an actuator that allows very slight displacement of the PDA by electrical control. Such an actuator may be often of the piezoelectric type, but may be also of the electrostatic attraction type, the ultrasonic type, the shape-memory alloy type, or the polymer stretching type. Especially among the actuators of the polymer stretching type, a polymer actuator using an ion conductive polymer, and a polymer actuator using a polymer hydrogel or a polymer organogel are light in weight, and cause a large amount of displacement. Due to such reasons, the polymer actuators as above have been actively under study. Examples include Patent Literatures 1 and 2 (Japanese Unexamined Patent Publication Nos. 2007-143300 and 2009-046649).
In Patent Literature 1, a polymer actuator using an ion conductive polymer is described as being configured to include a film made of ion-conductive polymer (film made of ion-exchange resin), and a pair of electrodes, for example. The ion-conductive polymer film is the one impregnated with a cationic substance, and the electrodes are formed on the surface of such a film. By application of a voltage between the pair of electrodes, the ion-conductive polymer film starts swelling or shrinking, and thus becomes curved in shape or deformed. In Patent Literature 2, a polymer actuator using a polymer hydrogel or a polymer organogel is described as being configured to include a three-dimensional (3D) cross-linked polymer, and a pair of electrodes, for example. The three-dimensional cross-linked polymer is impregnated with an electrolytic solution, and the electrodes are formed on the surface of the polymer. By application of a voltage between the electrodes, the 3D cross-linked polymer undergoes the oxidation-reduction reaction, and thus becomes curved in shape or deformed. Such polymer actuators may be lighter in weight and smaller in size, and thus may be applied to a PDA for use.
In the field of art, an attempt has been made to perform video display simultaneously with the formation of a protrusion pattern. An example includes Non-Patent Literature 1 (Yoichiro KAWAGUCHI, “Technology which Creates the Advanced Space of New Traditional Arts using Super High Resolution Images and Interactive Biological Objects”, [online], September 2007, Independent Administrative Institution Japan Science and Technology Agency [retrieved on Jul. 1, 2009], the Internet (URL:http://www.jst.go.jp/kisoken/crest/report/heisei18/html/mokuhyou/m okuhyou11.html)). For video display as such, a plurality of air cylinders provided on the rear surface of a screen are operated to form a protrusion pattern on the screen, and to project any video provided in advance separately onto the screen.